BS 13859-2:2010 pdf download – Flexible sheets for waterproofing — Definitions and characteristics of underlays Part 2: Underlays for walls 4.3.2.3 Class W3 If the product fails the test indicated in 4.3.2.2, e.g. the measured mean volume passing the specimens exceeds 100 ml, it shall be classified as resistant to water penetration Class W3. Untested products shall also be classified as resistant to water penetration Class W3. 4.3.3 Water vapour transmission properties The product shall be tested in accordance with 5.2.5 and the results shall lie within the declared tolerance of the manufacturer’s declared value. Other measuring methods shall also be allowed if the correlation with 5.2.5 is proved and recorded. If the water vapour diffusion-equivalent air layer thickness s d is above or equal to 0,2 m the product shall be tested in accordance with 5.2.5.1. If the s d value is below 0,2 m the product shall be tested in accordance with 5.2.5.2. If the s d value is below 0,1 m the standard deviation s shall also be recorded in the test report. 4.3.4 Resistance to penetration of air The product shall be tested in accordance with 5.2.6. The test result shall be given as air permeability, expressed in m 3 air per m 2 , hour at 50 Pascals pressure difference (m 3 /(m 2 × h × 50 Pa)). The value of air permeability shall be equal to or lower than the manufacturer’s limiting value. 4.3.5 Tensile properties The product shall be tested in accordance with 5.2.7 and the results shall lie within the declared tolerance of the manufacturer’s declared values for tensile strength and the maximum and/or minimum values for elongation for both longitudinal and transverse directions. 4.3.6 Resistance to tearing The resistance to tearing of underlays shall be tested in accordance with 5.2.8 and the results shall lie within the declared tolerance of the manufacturer’s declared value in both (longitudinal and transverse) directions. 4.3.7 Dimensional stability The dimensional stability shall be determined in accordance with 5.2.9. The shrinkage or lengthening shall be equal to or less than the manufacturer’s limiting value. 4.3.8 Flexibility at low temperature (pliability) Where appropriate, the flexibility at low temperature (pliability) determined in accordance with 5.2.10 shall be equal to or less than the manufacturer’s limiting value. 4.3.9 Artificial ageing behaviour The product shall be tested in accordance with 5.2.11. The mean values of tensile strength and elongation of...
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